Normally, in radio baseband LSI (Large Scale Integration), an equalization process of a received baseband signal is carried out, likelihood values are calculated from the equalization signal that is obtained as a result, and a received signal is then created by performing error correction using the likelihood values that were calculated.
When a likelihood value is calculated from an equalization signal, the calculation algorithm differs according to the modulation method. For example, modulation such as FSK (Frequency Shift-Keying), BPSK (Binary Phase-Shift Keying), QPSK (Quadrature Phase-Shift Keying), 8 PSK, 16 QAM (Quadrature Amplitude Modulation), and 64 QAM are frequently used in radio systems, and the likelihood value calculation algorithms differ for each of these modulation modes.
The modulation-type discriminating circuit described in Patent Document 1 is one example of a system provided with a likelihood value calculation circuit for each modulation mode. This modulation-type discriminating circuit is provided with a plurality of likelihood calculation units connected in parallel. Each of these likelihood calculation units corresponds to a modulation type that is the object of identification. The modulation type is inferred based on the likelihood value (cumulative addition value) that was calculated in each of the likelihood value calculation units.
In Patent Document 2, transmission diversity that uses a constellation rearrangement is described. In this transmission diversity, two versions are used in which the characteristics of the rules for mapping symbol data are assumed to be in a mutually complementary relation, first diversity signals being made up from modulated symbols corresponding to one version and second diversity signals being made up from modulated symbols corresponding to the other version. A diversity effect is obtained by averaging the likelihood values for the first and second diversity signals, and the error correction capability is improved.